No charges will be laid against four members of the South Canterbury Heartland rugby team caught up in an alleged rape last September in Whanganui.

Detective Senior Sergeant Neil Forlong said despite exhaustive inquiries, independent legal advice from Crown Law as well as their own legal team, it has been determined that there is insufficient evidence to support sexual assault or related charges being laid before the Court.

''However, should any new information come to light, police will consider this as appropriate.''

Forlong said it was a lengthy and methodical investigation which included more than 30 people being interviewed.

''The investigation team received full cooperation from all those spoken to. Regardless of the outcome, sexual assault is a serious crime and police are dedicated to thoroughly investigating all complaints reported to us."

A team of approximately 15 officers made up of staff from Whanganui, Palmerston North, and Timaru were working on the investigation at its height.

"We have also spoken with the young woman and her family and informed them of our investigation outcome," says Forlong.

In the wake of the original allegations, four South Canterbury players had voluntarily stood down from representative team, and have not been involved since.

The players had always denied any involvement in the alleged incident.